The present invention relates to a substrate for a light emitting diode (LED) used in an electronic instrument such as a portable telephone.
In recent years, it is required that the substrate for the LED has a high heat radiation property, heat-resistant property and high mechanical strength in accordance with the tendencies of a high performance, multifunction, small size of the electronic instrument.
FIG. 15 is a perspective view showing a conventional substrate for an LED. The substrate comprises a metal base 51 made of copper or aluminum, an insulation layer 52 of prepreg adhered on the metal base 51, circuit patterns 53 and 54 made of copper foil on which gold is plated. An LED 70 is mounted on the circuit pattern 53 and connected to the circuit pattern 54 by a wire 71.
The metal base 51 has a high heat radiation property.
FIG. 16 is a perspective view of another conventional double face substrate. The substrate comprises a pair of metal bases 61 made of copper, an insulation member 63 between the metal bases 61, insulation layers 62 of prepreg adhered to both sides of the metal bases 61, circuit patterns 64a and 64b made of copper foil on which gold is plated. An LED 72 is mounted on the circuit pattern 64a and connected to the circuit pattern 64b by a wire.
In the substrate of FIG. 15, circuit patterns can not be provided on the underside of the metal base 51. In the substrate of FIG. 16, since the insulation layer 62 is provided on the underside of the metal bases 61, the heat radiation property is insufficient.
An object of the present invention is to provide a substrate having a high heat radiation property.
According to the present invention, there is provided a substrate comprising a pair of metal bases, a first heat insulation layer disposed between the metal bases, a second heat insulation layer securely mounted on the metal bases, and mounting means for mounting an LED on the substrate.
The mounting means comprises a pair of circuit patterns securely mounted on the second heat insulation layer, the LED is securely mounted on both the circuit patterns.
In another aspect, the mounting means comprises a hole formed in the second heat insulation layer to expose surfaces of metal bases, the LED is securely mounted on both the metal bases.
The substrate further comprises upper and lower electrodes provided on an upper surface of the circuit patterns and on undersides of the metal bases.
One of the metal bases is different from the other metal base in size of a sectional shape.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.